JP2018197894A - Constant voltage power supply device - Google Patents

Abstract

To provide a constant voltage power supply device that can compensate the output voltage decrease caused by resistance elements of cables.SOLUTION: In the constant voltage power supply device including a transistor connected to the output terminal for voltage control and a control circuit, the control circuit is provided with a current mirror transistor (Q2) which is provided in parallel to the voltage control transistor (Q1) and generates reduced proportional current, current-voltage conversion means connected in series with the current mirror transistor, a voltage dividing circuit (12) that divides the output voltage of the output terminal, an error amplifier (11) that outputs the voltage in accordance with the electric potential difference between the divided voltage and the predetermined standard voltage, and a current-voltage conversion circuit that at least has an emitter follower circuit at the output part and converts the converted voltage to current via the current-voltage conversion means, and which compensates, in accordance with the output voltage the voltage supplied to the error amplifier by extracting from the voltage dividing circuit node, the current supplied by the current-voltage conversion circuit.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique that is effective when used in a DC power supply apparatus and a constant voltage power supply apparatus such as a series regulator for converting a DC voltage.

  There is a series regulator (hereinafter abbreviated as a regulator) as a power supply device that outputs a DC voltage of a desired potential by controlling a transistor provided between a DC voltage input terminal and an output terminal. As an application of such a regulator, there is a constant voltage power supply device (vehicle-mounted regulator) for supplying DC power to vehicle-mounted electronic devices such as an automobile car navigation device, ETC device, audio device, and antenna device.

In-vehicle regulators are required to have a role of providing an environment in which a DC power supply voltage is supplied to a desired part in a vehicle via a cable provided with a connector at the tip, and various electronic devices can be connected to the connector. There is.
However, when trying to realize the power supply function as described above, the length of the cable becomes relatively long. Therefore, when a current flows to the load through the cable, the voltage of the connector output decreases due to the resistance component of the cable. There is a problem.

In view of this, an invention relating to a device that compensates for a decrease in connector output voltage caused by a resistance component of a cable as described above in a vehicle-mounted regulator has been proposed (eg, Patent Document 1). In addition, an invention relating to a constant voltage power supply device as shown in FIG. 6A in which an output voltage compensation function is provided in order to compensate for a decrease in output voltage due to a resistance component included in a wiring for supplying a power supply voltage has also been proposed ( Patent Document 2).
Further, in FIG. 6B, an output voltage correction function is provided in order to suppress a decrease in the output voltage caused by the gate-source voltage of the differential input MOS transistor of the differential amplifier (error amplifier) constituting the regulator. An invention relating to a stabilized power supply circuit as shown in the drawings has also been proposed (Patent Document 3).

US Patent Publication 2016/0357204 JP 2014-10563 A JP 2002-91580 A

  The invention described in Patent Document 1 includes a differential amplifier circuit that inserts a current detection resistor in the middle of an output line, and detects and amplifies the voltage between both terminals of the current detection resistor, and the differential amplifier circuit A voltage-current conversion circuit having a voltage follower that receives the output of the output, and a node of a resistance voltage dividing circuit that divides the current converted by the voltage-current conversion circuit and generates a feedback voltage to a DC voltage regulator It is configured to be pulled out from. However, the present invention has a problem that power loss is large because a current detection resistor is inserted in the middle of the output line. In order to reduce power loss, it is conceivable to set the resistance value of the current detection resistor to a small value such as 0.2Ω. However, if this is done, the difference between detecting and amplifying the voltage between both terminals of the current detection resistor is considered. There is a need to increase the gain accuracy of the dynamic amplifier circuit, and the design and manufacture of such a high-accuracy circuit raises the problem of increasing the cost.

  Further, as shown in FIG. 6A, the constant voltage power supply device described in Patent Document 2 generates a current Io ′ proportional to the output current Io by the output transistor Q1 and the current mirror transistor Q2, The current is subjected to current-voltage conversion by a resistor R5, and a current Io ″ is generated by a voltage-current conversion circuit having an amplifier AMP2 that operates as a voltage follower. Then, a current mirror circuit CUR-1 generates a current Io '' 'proportional to Io' ', and causes the current to flow through the resistor R3 to generate a voltage drop ΔVi, which is used to control the output transistor Q1. 11 is input. Therefore, the use of current mirrors increases the number of elements and the consumption current, and the element variations accumulate and are amplified by the amplifier 11, so that the correction voltage by the compensation function is easily affected by the element variations. There are challenges.

  The stabilized power supply circuit described in Patent Document 3 generates a current Io ′ proportional to the output current Io by the output transistor Q1 and the current mirror transistor Q2, as shown in FIG. The current is folded by a current mirror and is extracted from the node N2 of the resistance voltage dividing circuit (R3, R2, R1) that generates the feedback voltage VFB to the amplifier AMP1 that controls the output transistor Q1. However, in this stabilized power supply circuit, there is a problem that the temperature characteristic of the resistor R3 affects the voltage for correcting the output, and the correction voltage changes due to temperature fluctuation.

The present invention has been made paying attention to the above-mentioned problems, and the object of the present invention is to provide a cable for supplying a power supply voltage without using a high-precision circuit that causes a small power loss and an increase in cost. An object of the present invention is to provide a constant voltage power supply device (voltage regulator) capable of compensating for a decrease in supply voltage caused by a resistance component.
Another object of the present invention is to provide a constant voltage power supply apparatus capable of accurately compensating for a decrease in output voltage due to a resistance component of an output line.
Still another object of the present invention is to provide a constant voltage power supply device that can eliminate a change in correction voltage due to temperature fluctuation.

In order to achieve the above object, the present invention provides:
A constant voltage power supply apparatus comprising: a voltage control transistor connected between a voltage input terminal to which a DC voltage is input and an output terminal; and a control circuit that controls the voltage control transistor according to an output feedback voltage. In
The control circuit includes:
A current mirror transistor that is provided in parallel with the voltage control transistor and flows a current proportional to the current flowing through the voltage control transistor;
Current-voltage converting means connected in series with the current mirror transistor;
A voltage dividing circuit for dividing the output voltage of the output terminal;
An error amplifier that outputs a voltage corresponding to a potential difference between the voltage divided by the voltage dividing circuit and a predetermined reference voltage;
A voltage-current conversion circuit which has an emitter follower circuit at least in the output section and converts the voltage converted by the current-voltage conversion means into a current;
The voltage generated by the voltage divider circuit and supplied to the error amplifier is corrected in accordance with the output voltage by drawing the current flowing through the voltage-current converter circuit from the node of the voltage divider circuit. It is composed.

According to the constant voltage power supply apparatus having the above-described configuration, the output line includes the current mirror transistor that generates a current that is proportional to the output current and the current-voltage conversion unit that is connected in series with the current mirror transistor. Because it is possible to detect the magnitude of the output current without providing a current detection resistor, the power loss is small, and the resistance component of the cable that supplies the power supply voltage is used without using a highly accurate circuit that increases costs. The resulting drop in supply voltage can be compensated.
In addition, since the current mirror circuit is not frequently used, it is difficult to be affected by element variations, and it is possible to accurately compensate for the decrease in output voltage due to the resistance component of the output line.

Preferably, the voltage control transistor, the current mirror transistor, the voltage dividing circuit, and the error amplifier are formed as a semiconductor integrated circuit on a semiconductor chip,
The semiconductor chip includes an external terminal to which a current output terminal of the current mirror transistor is connected,
The current-voltage conversion means is constituted by an external element having a small temperature characteristic connected to the external terminal.

  According to such a configuration, since the current-voltage conversion means is configured by an external element having a small temperature characteristic connected to the external terminal, the element configuring the emitter follower circuit and the element configuring the voltage dividing circuit are By using elements (resistors) having the same temperature characteristics, it is possible to prevent the correction voltage from having temperature dependency.

Preferably, the voltage-current conversion circuit includes a voltage follower in which a voltage current-voltage converted by the external resistor element is applied to an input terminal, and the emitter follower circuit.
The output voltage of the voltage follower is applied to the base terminal of the transistor that constitutes the emitter follower circuit.
According to such a configuration, it is possible to realize a circuit with a simple configuration and the correction voltage having no temperature dependence.

Further preferably, the emitter follower circuit includes a bipolar transistor having a collector terminal connected to the node of the voltage dividing circuit, and a resistance means connected to the emitter terminal of the transistor,
The resistance means includes a plurality of resistance elements connected in parallel, and the plurality of resistance elements are selectively connected to the emitter terminal.

  According to such a configuration, it is possible to generate a correction voltage having a desired characteristic by switching the resistance elements constituting the emitter follower circuit or changing the number of connected resistance elements. The correction voltage can be changed according to the length of the cable connected to the output terminal of the voltage power supply device, and the decrease in the supply voltage caused by the resistance component of the cable supplying the power supply voltage can be compensated with high accuracy.

  According to the constant voltage power supply device of the present invention, it is possible to compensate for a decrease in supply voltage caused by a resistance component of a cable that supplies a power supply voltage without using a high-precision circuit that causes less power loss and increases costs. Can do. Further, it is possible to accurately compensate for the decrease in output voltage due to the resistance component of the output line. Furthermore, according to the present invention, there is an effect that it is possible to eliminate the change in the correction voltage due to the temperature fluctuation.

It is a circuit block diagram which shows one Embodiment of the series regulator as a constant voltage power supply device to which this invention is applied. FIG. 2 is a circuit diagram showing a specific example of a voltage-current conversion circuit constituting an output voltage correction circuit in the regulator of the embodiment of FIG. 1. It is a graph which shows the relationship between the output current Io and the output voltage Vo in the regulator of this embodiment. It is a circuit diagram which shows the modification of the voltage-current conversion circuit which comprises an output voltage correction circuit. It is a circuit diagram which shows the modification of IC which comprises the regulator to which this invention is applied. (A), (B) is a circuit block diagram which shows an example of the conventional constant voltage power supply device which has an output voltage correction function.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.
FIG. 1 shows an embodiment of a series regulator as a constant voltage power supply device to which the present invention is applied. In FIG. 1, a portion surrounded by an alternate long and short dash line is formed as a semiconductor integrated circuit (regulator IC) 10 on a semiconductor chip such as single crystal silicon, and a capacitor is connected to the output terminal OUT of the regulator IC 10. It functions as a constant voltage power supply device that supplies a stable DC voltage. Further, the output terminal OUT is connected to the starting end of a power feeding cable having a connector at the tip.

  In the constant voltage power supply device of the present embodiment, as shown in FIG. 1, the voltage control device is a PNP bipolar transistor between a voltage input terminal IN to which a DC voltage Vin of the regulator IC 10 is applied and an output terminal OUT. Transistors Q1 are connected, and resistors R3, R2, and R1 constituting a voltage dividing circuit 12 that divides the output voltage Vo are connected in series between the output terminal OUT and a ground line to which the ground potential GND is applied. ing.

  The voltage at the connection node N1 between the resistors R1 and R2 constituting the voltage dividing circuit 12 is fed back to the non-inverting input terminal of the error amplifier 11 as an error amplifier circuit for controlling the base terminal of the voltage control transistor Q1. It is input as VFB. Then, the error amplifier 11 generates a voltage corresponding to the potential difference between the output feedback voltage VFB and the predetermined reference voltage Vref and supplies it to the base terminal of the voltage control transistor Q1 to control Q1 and output voltage Vo. Is controlled to a desired potential.

  Further, in the regulator IC 10 of this embodiment, a bipolar transistor Q2 that is connected in parallel with the voltage control transistor Q1 and forms a current mirror circuit with Q1 is provided, and a base terminal as a control terminal of the transistor Q2 Further, the same voltage as that applied to the base terminal of the voltage control transistor Q1 is applied. As a result, according to the element size ratio N, a current proportional to the collector current of Q1 (1 / n current) flows through Q2, where n is the current mirror ratio of the transistors Q1 and Q2. Yes. When the transistor Q1 is configured by connecting N transistors of the same size in parallel, and Q2 is configured by one transistor, the current is proportional to the number of elements.

Further, the regulator IC 10 is connected in series with the current mirror transistor Q2 between the voltage input terminal IN and a ground potential point outside the chip, and converts the collector current of Q2 into a voltage. An external terminal P1 for connecting the resistor R5 is provided.
Further, the regulator IC 10 is provided with an amplifier AMP having a non-inverting input terminal connected to the external terminal P1, and a connection node N2 between the resistors R1 and R2 constituting the voltage dividing circuit 12 and an internal chip. An NPN bipolar transistor Q3 and a resistor R4 constituting an emitter follower circuit are connected in series with the ground point.

  The output terminal of the amplifier AMP is connected to the base terminal of the transistor Q3, and the emitter terminal of the transistor Q3 is connected to the inverting input terminal of the amplifier AMP. Thus, the amplifier AMP functions as a voltage follower, and operates the transistor Q3 so that the emitter voltage of the transistor Q3 becomes equal to the input voltage of the non-inverting input terminal (potential of the external terminal P1).

  As the amplifier AMP, for example, as shown in FIG. 2, an input unit including transistors Q11 and Q12 and constant current sources CC1 and CC2, differential input transistors Q13 and Q14, active load transistors Q15 and Q16, and a constant current source CC3. And a differential amplifying circuit having an output part consisting of a transistor Q3 and a resistor R4 constituting an emitter follower circuit can be used. Note that the circuit shown in FIG. 2 is an example, and the circuit is not limited to the circuit having such a configuration.

  As described above, the current mirror transistor Q2 is supplied with the current Io ′ proportional to the collector current of the voltage control transistor Q1, that is, the current Io output from the output terminal OUT, and the current is supplied by the external resistor R5. Converted to voltage. Therefore, a correction current Io ″ proportional to the output current Io flows through the transistor Q3 constituting the emitter follower circuit. That is, the amplifier AMP and the emitter follower circuit (Q3, resistor R4) are voltage-current conversion circuits. The correction current Io ″ is extracted from the resistor R3 constituting the voltage dividing circuit 12.

  Therefore, when the output current Io increases, the collector current of the current mirror transistor Q2 increases, the potential of the external terminal P1 increases, the current flowing through the emitter follower circuit (Q3, resistor R4) increases, and flows through the resistor R3. The current increases. Then, the potential of the connection node N2 of the voltage dividing circuit 12, and hence the potential of the connection node N1, is lowered, the potential of the non-inverting input terminal of the error amplifier 11 is lowered, the output voltage of the error amplifier 11 is lowered, and voltage control is performed. The collector current of transistor Q1 will increase.

Specifically, when the reference voltage is Vref and the current mirror ratio of the transistors Q1 and Q2 is n (= Io / Io ′), the output voltage Vo is given by
Vo = (1+ (R2 + R3) / R1) * Vref + R3 * Io ”
= (1+ (R2 + R3) / R1) * Vref + ((R3 * R5) / (R4 * n)) * Io
As shown, the output voltage Vo is a voltage corresponding to the correction current Io ″.
That is, in the regulator according to the present embodiment, the current mirror transistor Q2, the external resistor R5, the amplifier AMP, and the emitter follower circuit (Q3, resistor R4) function as the voltage correction circuit 13.

  FIG. 3 shows the relationship between the output current Io and the output voltage Vo in the regulator of this embodiment. Here, (A) shows a connector in which a voltage drop has occurred due to the output current Io, the output voltage Vo of the output terminal OUT, and the voltage supplied to the load via the cable, that is, the resistance component of the cable, when there is no voltage correction circuit 13 Shows the relationship with the voltage Vo ′. (B) shows the relationship between the output current Io, the output voltage Vo of the output terminal OUT, and the connector voltage Vo ′ when the voltage correction circuit 13 is provided.

As apparent from FIG. 3A, in the absence of the voltage correction circuit 13, the voltage Vo ′ at the connector at the end of the cable decreases as the output current Io increases. On the other hand, when a voltage correction circuit is provided as in the regulator IC 10 of the present embodiment, the output voltage Vo at the output terminal OUT is increased as the output current Io increases as shown in FIG. Thus, the voltage Vo ′ of the connector at the end of the cable can be corrected to a desired voltage.
In addition, the correction amount can be changed by setting the resistance value of the resistor R5. As can be seen from the above equation, the correction amount is almost determined by the resistance ratio of the resistors R3 and R4, so that the correction amount can be easily calculated. Yes.

  Further, in the regulator of the present embodiment, an external terminal P1 is provided so that an external resistor can be used as the resistor R5 connected in series with the current mirror transistor Q2. Therefore, by using a discrete resistor having a small temperature characteristic as the external resistor R5, the correction amount by the voltage correction circuit 13 is set by the resistance ratio of the resistors R3 and R4 inside the chip, that is, an on-chip having a temperature characteristic. The temperature characteristic of the resistor R3 can be canceled by the temperature characteristic of R4, so that the correction amount does not have temperature dependency. Specifically, when the resistance value of the resistor R3 constituting the voltage correction circuit 13 decreases due to a change in temperature and the current increases, the resistance value of the resistor R3 configuring the voltage dividing circuit 12 also decreases and the current increases. The current flowing through the resistors R2 and R1 does not change, and the potential of the node N1 is constant regardless of the temperature change, and the correction amount by the voltage correction circuit 13 has no temperature dependence.

Further, although the voltage correction circuit 13 in the regulator of the present embodiment includes an amplifier AMP, this amplifier AMP functions as a voltage follower, and has a differential amplifier that performs an amplification operation as in the invention of Patent Document 1. There is no configuration. For this reason, since the correction amount of the output voltage is not related to the gain of the amplifier, it is not necessary to increase the accuracy of the gain, and an increase in cost due to the design and manufacture of a highly accurate circuit can be avoided.
Furthermore, since the regulator IC 10 of this embodiment does not have a configuration having a plurality of current mirror circuits as in the invention of Patent Document 2, there is an advantage that the configuration is simple and the number of elements and current consumption are small.

(Modification)
Next, a modified example of the regulator IC 10 of the embodiment will be described with reference to FIGS.
FIG. 4 shows a first modification of these. In this modified example, as a voltage correction circuit 13 provided in the regulator IC 10 of the above-described embodiment, a PNP having a collector terminal connected to a grounding point instead of the amplifier AMP in the previous stage of the output unit composed of the emitter follower circuit in FIG. A PNP-type emitter follower circuit comprising a bipolar transistor Q4 and a constant current source CC4 connected between the emitter terminal of the transistor Q4 and a power supply voltage terminal IN (or OUT) is provided. The constant current source CC4 may be a current mirror circuit or a resistance element.

FIG. 5 shows a regulator IC of a second modification. In this modification, the resistance R4 of the output section composed of the emitter follower circuit constituting the voltage correction circuit 13 in the embodiment of FIG. 1 is replaced with a plurality of parallel resistances R41, R42,... R4n, and a wiring pattern is formed. The resistance value is switched by connecting an arbitrary number of resistors by changing the photomask or cutting the formed wiring pattern with a laser. By switching the resistance value of the resistor R4, the slope of the output voltage Vo shown in FIG. 3B can be adjusted.
In addition, the resistor R4 may be replaced with a plurality of parallel resistors R41, R42,... R4n, and the transistor Q3 may be replaced with a plurality of parallel transistors so that an arbitrary number of transistors can be connected.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments. For example, in the above-described embodiment, the elements constituting the voltage correction circuit 13 and the voltage control transistor Q1 and the current mirror transistor Q2 are shown using bipolar transistors. However, MOSFETs are used instead of the bipolar transistors. You may make it do.
Moreover, although the case where the present invention is applied to a series regulator has been described in the above embodiment, the present invention can also be used for a DC-DC converter (switching regulator).

DESCRIPTION OF SYMBOLS 10 ... Regulator IC, 11 ... Error amplifier, 12 ... Voltage dividing circuit, 13 ... Voltage correction circuit, Q1 ... Voltage control transistor, Q2 ... Current mirror transistor

Claims (4)

A constant voltage power supply apparatus comprising: a voltage control transistor connected between a voltage input terminal to which a DC voltage is input and an output terminal; and a control circuit that controls the voltage control transistor according to an output feedback voltage. Because
The control circuit includes:
A current mirror transistor that is provided in parallel with the voltage control transistor and flows a current proportional to the current flowing through the voltage control transistor;
Current-voltage converting means connected in series with the current mirror transistor;
A voltage dividing circuit for dividing the output voltage of the output terminal;
An error amplifier that outputs a voltage corresponding to a potential difference between the voltage divided by the voltage dividing circuit and a predetermined reference voltage;
A voltage-current conversion circuit which has an emitter follower circuit at least in the output section and converts the voltage converted by the current-voltage conversion means into a current;
The voltage generated by the voltage divider circuit and supplied to the error amplifier is corrected in accordance with the output voltage by drawing the current flowing through the voltage-current converter circuit from the node of the voltage divider circuit. A constant voltage power supply device characterized by comprising. The voltage control transistor, the current mirror transistor, the voltage dividing circuit, and the error amplifier are formed as a semiconductor integrated circuit on a semiconductor chip,
The semiconductor chip includes an external terminal to which a current output terminal of the current mirror transistor is connected,
2. The constant voltage power supply device according to claim 1, wherein the current-voltage conversion means is constituted by an external resistance element having a small temperature characteristic connected to the external terminal. The voltage-current conversion circuit includes a voltage follower in which a voltage obtained by current-voltage conversion by the external resistance element is applied to an input terminal, and the emitter follower circuit.
3. The constant voltage power supply device according to claim 2, wherein an output voltage of the voltage follower is applied to a base terminal of a transistor constituting the emitter follower circuit. The emitter follower circuit comprises a bipolar transistor having a collector terminal connected to the node of the voltage dividing circuit, and a resistance means connected to the emitter terminal of the transistor,
The said resistance means is comprised by the some resistive element connected in parallel form, The said some resistive element is selectively connected to the said emitter terminal, The Claim 1 characterized by the above-mentioned. Constant voltage power supply.

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